Bacterial outer membrane vesicles induce plant immunity and enhance bacterial disease resistance
O. BAHAR (1) (1) Dept. of Plant Pathology and Weed Science, ARO - Volcani Centre, Israel

All Gram-negative bacteria pinch off portions of their outer membrane, releasing outer membrane vesicles (OMVs) to the surroundings. Strangely, the interactions between these highly abundant structures and plants have been mostly overlooked. In this study we sought to examine the interactions of OMVs and the plant immune system. We demonstrate that the cytosolic microbe associated molecular pattern (MAMP) EF-Tu is released to the outer cellular space in OMVs and that OMVs induce typical innate immune responses in Arabidopsis. Treating OMVs with proteinase K prior to Arabidopsis challenge did not reduce the level of defence gene activation indicating that non-proteinaceous immunogenic factors in OMV are being exposed to plant immune receptors. Nevertheless, Arabidopsis knockout lines lacking the immune receptors for peptidoglycan and lipopolysaccharides were sensitive to OMVs as wild type plants. To determine whether the elevated immune response imposed by OMVs would lead to bacterial disease resistance we pretreated Arabidopsis plants with OMVs and inoculated it with Pseudomonas syringe pv. tomato DC3000. A statistically significant reduction in DC3000 cell titer was observed in the OMV-pretreated plants compared with the water-pretreated control. Altogether, our results reveal a new facet in plant-bacteria interactions that may lead to new discoveries of the plant immune system and bacterial pathogenesis.

Abstract Number: P17-490
Session Type: Poster